Electromagnetically operated tapping device



April 21, 1970 J. F. DE MAYO 3,507,339

TROMAGNETICALLY OPERATED TAPPING DEVICE ELEC 3 Sheets-Sheet 1 Filed Aug.28, 1968 ELECTRIC PULSE GENERATOR c R c E L E Fllm PULSE GENERATOR J. F.DE MAYO 3,507,339

ELECTROMAGNETICALLY OPERATED TAPPING DEVICE 3 Sheets-Sheet 2 ""lii FIG.6

April 21, 1910 Filed Aug. 28, 1968 5 G l N w R I m a a A ril 21', 1910J. F. DE MAYO 3,507,339

ELECTROMAGNET I CALLY OPERATED TAPP ING DEVICE Filed Aug. 28, 1968 3Sheets-Sheet s United States Patent Ofiice 3,507,339 Patented Apr. 21,1970 3,507,339 ELECTROMAGNETICALLY OPERATED TAPPING DEVICE John F. DeMayo, 21 MacArthur Ave., Plainview, N.Y. 11803 Continuation-impart ofapplication Ser. No. 515,828, Dec. 23, 1965. This application Aug. 28,1968, Ser. No. 756,057

Int. Cl. B25d 13/00; G01] 7/20; B64d 43/00 US. Cl. 173100 10 ClaimsABSTRACT OF THE DISCLOSURE Means for cyclically tapping apparatus suchas an instrument having a movable element to relieve static friction andthereby keep the movable element from sticking comprises a base which issecured to the apparatus, a pad on the base, a movable hammer arrangedto strike the pad and an electromagnet which is periodically energizedto cause the hammer to strike the pad and thereby impart periodicmechanical impulses to the base and to the apparatus to which it issecured.

This application is a continuation-in-part of my application Ser. No.515,828 filed Dec. 23, 1965, and now abandonded.

This invention relates to an apparatus for tapping an instrument orother apparatus having a movable element, to prevent the movable elementfrom sticking.

The apparatus having the movable element may be, for example, anindicator apparatus having a movable indieating element or a hydraulicor penumatic valve having movable means for closing, opening oradjusting to an intermediate position of the valve. The term tapping anapparatus as used herein does not refer only to direct tapping of theapparatus having the movable element but refers to any tapping effectedby the apparatus of the invention provided that the mechanical impulsesresulting from the tapping are transmitted to the apparatus having themovable element.

In the further discussion of the invention which follows, the stickingof the indicating element of an indicator apparatus will be referred to.However, it is to be understood that the invention is applicable to anyapparatus having a movable element in which the movable element tends tostick.

The indicating element, such as a needle, of an indicator apparatus,such as an airplane altimeter, frequently tends to stick. The cause ofthe sticking is frequently static friction or static electricity;however, in describing the invention the cause of the sticking is notimportant. It is relevant to know only that the sticking of theindicating element can be avoided or remedied by subjecting theindicator apparatus to tapping. The tapping may be directly upon theindicator apparatus itself or it may be upon the instrument panel orother means mounting the indicator apparatus.

The sticking of an altimeter is referred to above because theconsequences of the sticking of the indicator element in this indicatorapparatus can be particularly serious. Thus, if the altimeter of anairplane incorrectly indicates the altitude because of sticking of theindicating element a crash may result. Especially in the case of jetpowered airplanes this can be a serious problem, for in such airplanesthere is relatively little engine vibration to free a stuck indicatingelement or to prevent the sticking of the indicating element. However,it will be appreciated that the invention is not limited in itsapplicability to airplane altimeters only.

According to the invention there is provided an apparatus for tapping anapparatus having a movable element to prevent the movable element fromsticking, the essential elements of the apparatus for tapping being anelectromagnet, an armature pivotally mounted with at least a portionwithin the magnetic field defined by the electromagnet when theelectromagnet is energized, and a pad disposed in the path of movementdefined by the armature when the electromagnet is energized and thearmature is attracted by the magnetic field and moves toward theelectromagnet. In its movement toward the electromagnet the armaturetaps the pad. The mechanical impulses of this tapping may be transmittedto the apparatus having the movable element; for example, in thisinstance of an indicator apparatus, this may be accomplished by havingmounted the tapping apparatus on the back of the indicator apparatus orby having mounted the tapping apparatus on an instrument panel on whichthe indicator apparatus is mounted or by any equivalent arrangementproviding for the transmission of the impulses to the indicatorapparatus.

The coil of the electromagnet may be connected to electrical impulsegenerating means. The electrical impulses periodically energize theelectromagnet, causing the electromagnet to attract the armature, andthe armature in its movement toward the electromagnet strikes the abovereferred to pad thereby etfecting a single tap.

By providing for return of the armature to its initial or rest positionwhen the energization of the electromagnet is discontinued orinterrupted, i.e., when the electromagnet is deenergized, periodictapping, corresponding in frequency to the frequency of the electricalenergizing impulses, is attained. The duration and the frequency of theelectrical energizing impulses may be selected to best overcome thesticking problem of the particular indicator apparatus for theparticular conditions :of use of the indicator apparatus. For example,where the apparatus having a movable element is an airplane altimeterhaving movable indicator needle, effective preventing of sticking of theindicator needle may be obtained with apparatus according to theinvention provided with electrical energizing impulses each of about 15to 20 milliseconds in duration with deenergization intervals of about 30milliseconds in duration. However, the duration and spacing of theenergizing impulses may be varied with operating conditions.

Return of the armature to its rest position when the electromagnet isdeenergized may be eifected by gravity if the tapping apparatus ismounted in its operating position so that the rest position of thearmature is lower than the position of the armature when the armaturetaps the pad. However, more generally, return of the armature iseffected by the provision of spring means biasing the armature away fromthe electromagnet. When the electromagnet is energized, it attracts thearmature strongly enough to overcome the opposition of the spring means,however, thereby tensioning the spring means. When the electromagnet isdeenergized the tensioned spring means moves the armature back to itsrest position. The rate at which the force of the spring increases asthe armature is moved by the electromagnet is selected so as to assurethat the armature does not stick, for example by reason of residualmagnetism, while minimum resistance is offered by the spring atthebeginning of the movement.

A member may be provided to limit the extent of movement of the armatureaway from the electromagnet when the electromagnet is deenergized. Thismember is disposed in the path of movement of the armature away from theelectromagnet so that it blocks movement of the armature away from theelectromagnet so that the armature may move only a certain predetermineddistance from the armature. Thus, for example, in a tapping apparatusaccording to the invention for an airplane altimeter, the member whichlimits upward movement of the armature may be positioned so that thearmature cannot move more than on the order of a tenth of an inch fromthe electromagnet; this numerical value is only exemplary. The restposition of the armature will not necessarily be against the memberwhich limits upward movement of the armature provided the armatureprevents excessive springing back of the armature. Means may be providedfor adjusting the distance between the member and the electromagnet sothat the maximum movement of the armature away from the electromagnetmay be set to any desired magnitude.

Means may be provided for adjusting the distance between the part of thearmature which strikes the pad and the pad. Thus, for example, it may beprovided that the armature include a hammer member which taps the padand the hammer member may be provided with means to extend it toward orwithdraw it from the pad so that depending upon the setting of thehammer the distance through which the armature will move from its restposition to a position at which the hammer member taps the pad will bedetermined.

The invention will now be further described by reference to thedrawings, in which:

FIG. 1 is a plan view of a first embodiment of an apparatus according tothe invention;

FIG. 2 is a sectional view of the embodiment of FIG. 1 taken alongsection line 2-2;

FIG. 3 is a sectional view of the embodiment of FIG. 1 taken alongsection line 33;

FIG. 4 is an elevation view of a second embodiment of an apparatusaccording to the invention.

FIG. 5 is a plan of a further embodiment of the invention.

FIG. 6 is a sectional view taken along the section line 6-6 in FIG. 5.

FIGS. 7 and 8 are sectional views taken along the line 88 in FIG. 5 andillustrating steps in initially adjusting the apparatus.

FIG. 9 is a side view of another embodiment of the invention.

FIG. 10 is a plan view of the embodiment shown in FIG. 9, and

FIG. 11 is a circuit diagram of a circuit for supplying intermittentpulses for energizing the magnet.

In the embodiment illustrated in FIGS. 1 to 3, an armature 10 ispivotally mounted on a support for movement relative to an electromagnet11. The support 15 is mounted on a base plate 21. The electromagnet 11is mounted on the same base plate 21 by means of a stud 22. The baseplate 21 is provided with slots to receive suitable screws or bolts 21afor securing it to the instrument or other apparatus on which thetapping device of the present invention is mounted. A portion of thecasing of such apparatus is illustrated in FIG. 2 and designated A.

The pivotal mounting of the armature 10 on the support 15 is effected bymeans of a pivot 14. A spring 13 is attached at one end to a pin 23mounted in the support 15 and at its other end to an extending endportion of the armature 10.

The magnetic core 18 is mounted in the hollow center of a bobbin 20.Around the bobbin 20 is wound a coil 19 of electrically conductive wire.The coil is connected to electric impulse generating means G (FIG. 1).

A limit member 16 for limiting the upward movement of the armature ismounted with a tongue 26 on an adjustment screw 27 by means of a pin 24passing through a hole in each of the limit member 16 and the tongue 26,the pin 24 being joined at one end to the adjustment screw 27 and at itsother end mounting a collar 25. The adjustment screw 27 is mounted in atapped hole in a support 28 and the support 28 is mounted in the baseplate 21. The support 28 is provided with a slot or channel 29 in whichthe tongue 26 fits. The tongue 26 is held in place in the slot 29 bymeans of a retaining ring 30 which is set in a groove about thecircumference of the support 28.

As shown in FIGS. 1 to 3, the armature 10 includes a support 34 mountinga hammer member 17. The hammer member has a head 31 and a threaded shaft32. The threaded shaft 32 fits into a tapped hole in the support 34. Theend of the shaft 32 opposite the head 31 is provided with a slot 33 toaccommodate a screwdriver. The pad 12 is disposed below the hammermember head 31 in a recess in the base plate 21.

When the electromagnet 11 is energized by means of an electrical impulsefrorrf the electrical impulse generating means G, the armature 10, whichinitially is in its rest position as illustrated in the drawings, isattracted by the electromagnet, since at least a portion of the armaturewhen in its rest position is disposed within the magnetic field of theenergized electromagnet. The armature 10 therefore moves about the pivot14 toward the electromagnet, its movement tensioning the spring 13,until the hammer member carried by the armature taps against the pad 12on the base plate 21.

The electromagnet 11 is then deenergized by discontinuing orinterrupting the energizing impulse from the electrical impulsegenerating means. The output of the electrical impulse generating meansmay be, on a plot of current versus time, an approximately square wavehaving periodic minima, which may be zero or essentially zero, theoccurrence of these minima being referred to as discontinuing orinterrupting the energizing impulse; in other words, at the least thecurrent decreases to a level at which it does not cause theelectromagnet 11 to produce a magnetic field strong enough to hold thearmature 10. When the electromagnet 11 is deenergized, the tension inthe spring 13 draws the armature 10 away from the electromagnet 11. Thearmature 10 may, due to momentum, continue past its rest position.However, the limit member 16 will block movement of the armature 10excessively past its rest position.

The distance between the limit member 16 and the electromagnet 11 may beadjusted by means of the adjustment screw 27, thereby to adjust theextent, if any, the armature is allowed to move past its rest position.

The distance between the rest position of the. hammer member 31 (FIGS. 1to 3) and the pad 12 may be adjusted by using a screwdriver in the slot33 of the shaft 32, the threaded shaft 32 of the hammer member 31thereby functioning in cooperation with the tapped hole in the support34 as, in effect, an adjustment screw which is part of the hammer member31 itself.

The purpose of the pad is to absorb any excessive mechanical impulses orshock which might be produced if the armature were to tap a hardmetallic or plastic surface. Accordingly, the material for the padshould be less hard than materials such as iron or steel or hardplastics such as nylon. However, it is not intended that the padfunction as a cushion in the sense of being highly resilient;accordingly, the material of which the pad is made need not beparticularly resilient. Typical of the materials of which the pad may bemade are hard cured rubbers including synthetic rubbers. An example of asuitable material for the pad is a silicone rubber cured with dibutyltin dilaurate and having a durometer hardness on the Shore A scale ofabout 40 to 70; such silicone rubbers are well known and are describedfor example in Technical Data Book S3C of the General Electric Company.Another suitable material is Buna N having a hardness in the same range.The pad may be quite thin, and thus may be in the form of a film or thinsheet or disc material. In the embodiments shown in the drawings the padhas a thickness which is about .010" to .020" and preferably about.015". The pad is secured, for example by adhesive, in a recess in thebase with its upper face approximately flush with the adjacent surfaceof the base. However, the upper face of the pad may project slightly,for example about 0.00 above the base surface.

Another embodiment of the invention is illustrated in FIG. 4 in whichlike parts are designated by the same reference numerals as in FIGS. 1to 3 and corresponding but somewhat different parts are designated bythe reference numerals with a prime added. The electromagnet 11 ismounted on the base plate 21 by means of a mounting screw 22' whichextends through a washer 22a and is screwed into a tapped hole in thepole piece 18' of the electromagnet. An armature 10' is pivotallymounted at one end on an upstanding support 15 by a hinge connection 14.At the other end of the armature 10, there is provided a hammer portion17' adapted to strike a pad 12' which is received in a recess in theupper end of a cylindrical upstanding portion 21b on the base 21. Theparts are so proportioned that the armature 10' will not strike the polepiece 18' of the electromagnet before the hammer portion 17' strikes thepad 12. However, to avoid any possibility of metal-to-metal contactbetween the armature and the electromagnet, there may be provided on thetop of the latter a layer 18a of non-metallic material, for example, aplastic or rubber composition.

The embodiment illustrated in FIG. 4 operates in the same manner as thatof FIGS. 1 to 3. When the electromagnet 11 is periodically energized bya pulse generator G, the armature 10 is attracted toward theelectromagnet, causing the hammer portion 17' to strike the pad 12provided on the upwardly projecting portion 21b of the base plate 21.The impulse resulting from the impact of the hammer portion 17' with thepad 12' is transmitted through the base plate to the instrument or otherapparatus on which the base plate is secured. In the intervals betweenenergization of the electromagnet, the armature 10' is moved away fromthe electromagnet by the spring 13. As in the first embodiment, outwardmovement of the armature 10' is limited by the limit member 16.

In a further embodiment illustrated in FIGS. to 8, an electromagnet 40comprising an annular coil 41 wound on plastic bobbin 41a andsurrounding a pole piece 42 which is secured to a base plate 43 by astud 42a on the pole piece extending through an opening provided in thebase plate. A flange 4212 on the pole piece secures the coil in lace. Anarmature 44 is pivotally mounted on a support member 45 projectingupwardly from the base plate by means of a pin 46 which projectslaterally from opposite sides of the armature and is received in notchesprovided in the upper end of the support 45. The width of the armatureis approximately equal to the diameter of the pole piece 42. A hammerportion 47 provided on the opposite end of the armature '44 is adaptedto strike a pad secured in a recess in the upper face of the base plate43. A spring 50 acting between a projecting end portion of the armature44 and a pin 51 on the support 45 acts to move the armature away fromthe electromagnet when the latter is not energized. Upward movement ofthe armature is limited by engagement with the end of a screw 52 whichis screwed through a tapped hole in a U-shaped bracket 53 which extendsover the electromagnet and armature as seen in FIG. 6 and has oppositeend portions secured to the base plate 43, for example, by screws 54.

When the tapping device is initially assembled, the screw 52 has a headportion 52a by which the screw can be rotated to adjust it upwardly ordownwardly relative to the supporting bracket 53. Adjustment of thescrew 52 controls the length of the stroke of the hammer 42 and therebythe force of the impact with which it strikes the pad 48 on the baseplate 43. When the screw 52 has been adjusted to provide the desiredimpact force, it is cut off as seen in FIGS. 6 and 8 and soldered inplace. A nonmetallic layer 55 formed for example of rubber or plasticcomposition is provided on the upper face of the armature 44 to avoidmetal-to-metal contact between the armature and the screw 52.

The operation of the embodiment shown in FIGS. 5 to 8 is the same asthat described with reference to FIGS. 1 to 3. When the electromagnet 40is energized by the pulse generator G, the armature 44 is attractedtoward the electro-magnet, causing the hammer 47 to strike the pad 48 onthe base plate 43 and thereby transmit a pulse to the apparatus on whichthe device is mounted. The rate of the spring is selected so as to offeronly small resistance as the armature begins its movement toward theelectro-magnet but to exert sufficient force on the armature at the endof the stroke to avoid the possibility of the armature sticking byreason, for example, of residual magnetism in the core 42. For example,the spring may exert a force of 2 to 4 grams on the armature when in itsupper position and 25 grams to the end of the downward stroke.

In order to provide an efiicient and effective magnetic circuit, thepole piece 42, base plate 43, upright 45 and armature 44 are of highpermeability magnetic material. The bracket 53 and screw 52 arepreferably of nonmagnet material, for example, brass. The hammer 47 maybe formed of non-magnetic material such as brass or alternatively may beof magnetic material such as iron so as to form a part of the magneticcircuit.

In FIGS. 9 and 10, there is shown a further embodiment of the inventionin which an electro-magnet having a core piece surrounded by an annularcoil is mounted on a base plate 63 having holes 63a and 63b to receivescrews or bolts for securing it to an instrument or other apparatus onwhich the device is mounted. An armature 64 is pivotally mounted nearone end on a support 65 projecting from the base. The pivot comprises apin 66 extending through and projecting laterally from the armature andhaving portions received in notches at the upper end of the support 65.A hammer 67 carried by the opposite end of the armature 64 is adapted tostrike a pad 68 secured in a recess in the upper surface of the baseplate 63. Return movement of the armature is provided by a spring 70extending between a stud 71 on the support 65 and a projecting endportion of the armature 64. Upward movement of the armature is limitedby a stud 72 screwed through a threaded opening in a U- shaped bracket73 which extends up over the electromagnet and the armature and has itslower ends secured to opposite sides of the base plate. A layer ofrubber or plastic material 75 on the upper face of the armature 64prevents metal-to-metal contact between the armature and the lower endof the stud 72. The operation of the embodiment shown in FIGS. 9 and 10is the same as has already been described.

The apparatus in accordance with the present invention differs from avibrator in that the armature 10 carrying the hammer 17 (with referenceto FIGS. 1 to 3) is not continuously in motion but is actuated atselected intervals spaced by rest periods in which the armature is inits upper or relaxed position. Accordingly, the pulse generator Gsupplies current pulses to the coil 19 of the electromagnet 11 atcorrespondingly spaced intervals,

the electromagnet being deenergized during the rest period. The periodduring which the electromagnet is energized should not exceed the periodduring which it is deenergized and should preferably be less. Preferablythe electro-magnet is energized for a period sufficient to cause thehammer to strike the pad and is deenergized the rest of the time. Forexample, if the electromagnet is to be energized 20 times a second, theperiod during which the electromagnet is energized is preferably 15 to20 milliseconds and the period during which the electromagnet isdeenergized is 35 to 30 milliseconds. The electromagnet is preferablyenergized by pulsating direct current with an approximately square waveform and a voltage which is preferably of the order of 24 to 32 volts.

An example of a suitable electric pulse generator is illustrated in FIG.11. The circuit shown is a DC multivibrator comprising two transistorsand 81. The bases of the transistors are connected to a positive voltageline 82 through resistors 83 and 84 respectively. The emitters of thetransistors are connected to a negative coltage line 85 through diodes86 and 87 respectively. The collector of transistor 80 is connected tothe positive line 82 through a resistance 88 and is also connectedthrough a capacitor 89 to the base of the transistor 81. The collectorof transistor 81 is connected through a capacitor 90 to the base of thetransistor 80 and is also connected through the coil of theelectromagnet (here designated coil 19) to the poistive line 82. A diode91 protects the circuit against any back EMF of the coil. The circuit isconnected to a power supply through a voltage dropping resistance 92 anda diode 93. The diode 93 acts as a rectifier so that the circuit can beoperated from an alternating current power supply as well as a directcurrent. When the circuit is operated from a DC power supply, the diode93 protects it against accidental reversal of polarity. Capacitors 94and 95 are connected across the line as decoupling filters.

With the circuit shown, the transistors 80 and 81 are alternatelyconductive. When the transistor 81 is conductive, current is supplied tothe electromagnet coil 19 to energize the coil. When transistor 80 isconductive, the coil is deenergized. The periods during which therespective transistors are conductive is determined by suitableselection of the RC characteristics of the circuit. Although theelectromagnet coil has been designated by the reference numeral 19 inFIG. 11, it will be understood that the circuit shown can be used withany of the devices illustrated.

While for convenience of description, reference has been made to upwardand downward movement and direction, it will be understood that theapparatus in accordance with the invention can be mounted and operatedin any desired position. The modification shown in FIG. 4 isparticularly suitable for mounting in an inverted position from thatshown in the drawings since the hammer 17' is of less mass and henceless affected by the force of gravity. Insofar as they are compatible,the various characteristics and features of the several embodimentsillustrated in the drawings are mutually interchangeable. Moreover,other variations can be made in details of construction, the illustratedembodiments being shown merely by way of example.

I What I claim is:

1. Means for cyclically tapping an apparatus having a movable element torelieve static friction and thereby prevent the movable element fromsticking, comprising a base having means for securing said base to saidapparatus', non-metallic impact pad means on said base; hammer means forstriking said pad means; means on said base for pivotally mounting saidhammer means for free movement into and out of engagement with said padmeans; means for actuating said hammer means comprising an electromagnetmounted on said base and having a coil and a pole piece, an armaturecomprises in said hammer means and attracted to said pole piece whensaid electromagnet is energized and means biasing said armature to moveaway from said pole piece when the electromagnet is deenergized; meanslimiting movement of said armature away from said pole piece, and pulsegenerator means for periodically energizing said electromagnet atregular intervals to actuate said hammer means to strike said pad meansperiodically and thereby transmit periodical mechanical impulses tosaidbase and from said base to said apparatus to relieve static friction andthereby free said movable element.

2. Tapping means according to claim 1, in which said limiting meanscomprises means for varying the stroke of said hammer means and therebyvarying the force of impact of said hammer means on said paid means.

3. Tapping means according to claim 1, in which nonmetallic resilientimpact damping means is disposed between said armature and said limitingmeans to avoid a 8 metal-to-metal impact between said armature and saidlimiting means.

4. Tapping means according to claim 1, in which base, mounting means,armature and pole piece are of magnetic material having highpermeability and said limiting means comprises non-magnetic material.

5. Tapping means according to claim 1, in which said armature ispivotally mounted intermediate its ends, and in which said hammer meanscomprises a hammer carried by one end portion of the armature and saidbiasing means comprises a tension spring attached to an opposite endportion of the armature.

6. Tapping means according to claim 1, in which the duration of saidpulses is less than that of the intervals between successive pulses.

7. Tapping means according to claim 1, in which said armature comprisesa bar of magnetic material disposed approximately parallel to said base,pivotally supported at one end by said mounting means, extending acrosssaid pole piece and having a free end extending beyond saidelectromagnet, and in which said hammer means comprises said armatureand a hammer portion carried by the free end of said armature andextending toward said base.

8. Tapping means according to claim 7, in which said pad means comprisesa layer of synthetic material secured on a portion of the base inposition to be struck by said hammer portion.

9. Tapping means according to claim 8, in which said portion of the baseis recessed and a free surface of said synthetic material isapproximately flush with the adjacent surface of said base.

10. Means for cyclically tapping an apparatus having .a movable elementto relieve static friction and thereby prevent the movable element fromsticking, comprising a base having means for securing the base to saidapparatus; non-metallic pad means on said base; hammer means forstriking said pad means comprising an armature pivotally mounted on saidbase and a hammer carried by said armature in position to strike saidpad means; an electromagnet mounted on said base in position to attractsaid'armature when said elcctromagnet is energized to actuate saidhammer to strike said pad means, means biasing said armature to movesaid hammer away from said pad means; means limiting movement of saidhammer away from said pad means including non-metallic impact dampingmeans engageable by said hammer means; and pulse generator means forperiodically energizing said electromagnetic means at regular intervalsto actuate said hammer means periodically to strike said pad means andthereby transmit periodical mechanical impulses to said base and to saidapparatus on which said base is secured to relieve static friction andthereby free said movable element.

References Cited 7 UNITED STATES PATENTS 2,396,383

ERNEST R. PURSER, Primary Examiner U.S. C1. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 507339 Dated April 21 1970 Inventor) John F. De Mayo It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 7, line 53, delete "comprises" and insert -comprised-.

Signed and sealed this 10th day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents I i g FORM po'wso (1069) USCOMM-DC eons-Pen

